Hydraulic cylinder



Nov. 7, 1967 D. A. JOHNSON HYDRAULIC CYLINDER 3 Sheets-Sheet 1 FiledJan. 12, 1966 FIG.

INVENTOR. DELL A. JOHNSON BY EM D. QM:-

ATTORNEY Nov. 7, 1967 D. A. JOHNSON 3,350,987

HYDRAULIC CYLINDER Filed Jan. 12, 1966 3 Sheets-Sheet '2 FIG. 3

I NVENTOR. DELL A JOHNSON BY W ATTORNEY D. A. JOHNSON 3,350,987

HYDRAULIC CYLINDER Nov. 7, 1967 3 Sheets-Sheet 5 Filed Jan. 12, 1966 QM"Q 32 m FIG. 4

INVENTOR.

DELL A. JOHNSON FIG.5

BY Magma;-

ATTORNEY United States Patent C) 3,350,987 HYDRAULIC CYLINDER Dell A.Johnson, Nihley, Utah, assignor to Thiolrol Chemical Corporation,Bristol, Pa., a corporation of Delaware Filed Jan. 12, 1966, Ser. No.520,153 2 Claims. (Cl. 92-24) This invention relates to a fluid pressureactuator and locking device, and more particularly to a hydrauliccylinder having an extensible shaft that can be locked in variableposition relative to the casing of said hydraulic cylinder.

lthough hydraulic cylinders have been Widely used as the actuatingmechanisms of various holding devices, their use in such apparatus hascertain disadvantages For example, if the pressure applied against thepiston of a conventional hydraulic cylinder used in a holding device isnot maintained at a constant level, a workpiece or other article can beprematurely released from the holding device with disastrousconsequences. The present invention provides a hydraulic cylinder havingan internal locking mechanism that holds the piston of said cylinder inany desired position along its range of travel, leakage of hydraulicfluid past said piston or even complete loss of fluid pressure in saidhydraulic cylinder having no effect on the locked condition of thepiston after a shaft connected thereto has been moved against aworkpiece or other body that is to be held in fixed position. As will beexplained in detail hereinafter, this advantageous locking arrangementis achieved by means of a hydraulic cylinder comprising a shell slidablydisposed within the casing therof, a piston slidably disposed withinsaid shell and connected to a hollow shaft that extends throughapertures in said shell and casing respectively, and one or more lockingwedges carried by said shell and adapted to engage the wall of anopening in said piston and the surface of a projection that is connectedto said casing and coaxially disposed therein. For reasons that willbecome manifest in the following specification of the invention, theaforementioned shell and piston each contain a vent passage in which isdisposed a check valve permitting fluid flow in one directiontherethrough.

It is accordingly an object of this invention to provide a fluidpressure actuator and locking device having an extensible shaft that canbe locked in variable position relative to the casing of said device.

Another object of this invention is to provide a fluid pressure actuatorand locking device having an extensible shaft that can be moved to aselected position relative to the casing of said device by means offluid pressure introduced into one end of said casing automaticallylocked in said position, and subsequently unlocked by means of fluidpressure introduced into the other end of said casing.

Other objects and advantages of the present invention will becomeapparent in the following specification thereof, in which reference ismade to the accompanying drawings, wherein:

FIGURE 1 is a pictorial view illustrating a preferred embodiment of theinvention, portions of certain of the components of said embodimentbeing cut away for clarity;

FIGURES 2, 3 and 4 are longitudinal sectional views of the preferredembodiment of the invention, illustrating the relation of its componentsin different operational positions thereof; and

FIGURE 5 is a cross-sectional view of the preferred embodiment of theinvention, taken along the plane represented by line 5-5 of FIGURE 4.

Throughout the specification and drawings like reference numbers referto like parts.

The preferred embodiment of this invention illustrated in FIGURE 1comprises a cylindrical casing 10 having first and second end closures12, 14 respectively attached to opposite ends thereof. Morespecifically, as can be seen in FIGURE 2 end closure 14 is integrallyjoined to casing 10, whereas end closure 12 is threadedly engaged withsaid casing. End closure 12 has an aperture 16 formed therein, thecentral axis said aperture being coincident with the longitudinal axisof casing 10 and a circumferentially extending groove 18 being formed inthe Wall of said aperture 16 to accommodate a seal ring 20. At each endof casing it there is a fluid pressure port 22, 24. Disposed withincasing 19 is a projection, generally designated by reference number 26,which has the form of a truncated pyramid that is square incross-section. The longitudinal axis of projection 26 is coincident withthe longitudinal axis of casing 10, and the large end of said projectionis fixedly connected to end closure 14, as by means of being weldedthereto. Thus each of the four planar surfaces 28- of projection 26 isconvergent with respect to the longitudinal axis of casing lit in thedirection of end closure 12.

A cylindrical shell 30 is slidably disposed within casing 10, said shellhaving first and second end walls 32, 34 which are respectively attachedto opposite ends thereof. More specifically, end wall 3 is integrallyjoined to shell 30, whereas end wall 32 is threadedly engaged with saidshell. Each of the end walls 32, 34 includes an aperture 36, 38 throughwhich projection 26 extends, the walls of said apertures beingrespectively spaced from surfaces 23 of said projection. End wall 32also has a vent passage 4% formed therein. Shell 30 is provided with acircumferentially extending groove 42 in which is positioned a seal ring4-4, and with a longitudinally extending groove 46 which faces the innersurface of casing 16. A pin 48 is fixedly mounted in a hole that extendsthrough the wall of casing 19 intermediate end closures 12, 14, theinner end of this pin being slidably disposed in groove 46 and thusserving to prevent rotation of shell 30 relative to said casing.

A piston 50 is slidably disposed within shell 30, said piston havingformed therein an opening 52 which is pyramidal in shape and throughwhich projection 26 extends. More particularly, opening 52 has fourplanar Wall surfaces, is square in cross-section, and. its longitudinalaxis is coincident with the longitudinal axis of casing 10. The largeend of opening 52 faces end Wall 34, and each of its Wall surfaces isdisposed opposite, and spaced from, a respective one of the surfaces 28of projection 26. Thus the wall surfaces of opening 52 are alsoconvergent with respect to the longitudinal axis of casing 10 in thedirection of end closure 12, and more specifically, as can be seen inFIGURES 2, 3, and 4, said wall surfaces are inclined at a slightlygreater angle with respect to the longitudinal axis of casing 10 thanare surfaces 28 of projection 26. Piston 50 also has a vent passage 54formed therein, the portion 56 of said vent passage that is adjacent endwall 32 having an increased diameter and the portion 58 of said ventpassage that is adjacent end wall3 i being convergent in the directionof end wall 32. A seal ring 60 is positioned in a circumferentiallyextending groove 62 formed in the peripheral surface of piston 50.

Slidably disposed within aperture 36 in end wall 32 and aperture 16 inend closure 12 is a hollow cylindrical shaft 64. The outer end of shaft36 is closed by a bulkhead 66, and the inner end of said shaft isfixedly connected to piston 50, as by means of being welded thereto.More specifically, the inner end of shaft 64 surrounds the opening 52 inpiston 50, and thus the interior 68 of said shaft communicates with saidopening.

Coaxially disposed Within shell 30 is a frustoconical guide member 70the large end of which is integrally joined to end wall 34. Fourrectangular slots 72 are formed in guide member 70 adjacent the free endthereof, these slots being evenly spaced circumferentially of said guidemember and equidistant from end wall 34. Projection 26 extends throughguide member 70 in spaced relation therewith, and four locking wedges,each of which is generally designated by reference number 74, arerespectively slidably disposed in the slots 72 in said guide member andthus can be moved in a direction perpendicular to the longitudinal axisof casing 10. The inner surface 76 of each locking wedge 74 is planarand disposed adjacent a respective one of the surfaces 28 of projection26, and the outer surface 78 of each locking wedge is also planar anddisposed adjacent a respective one of the wall surfaces of the opening52 in piston. Thus the outer surface 78 of each locking wedge 74 is alsoconvergent with respect to the longitudinal axis of casing in thedirection of end closure 12. As can be seen by inspection of FIGURES 2,3 and 4, the lengths of casing 19, shell 30, projection 26, guide member70 and locking wedges 74 are such that a portion of the wall of theopening 52 in piston 50 is disposed opposite locking wedges 74 in anyposition of piston 50 relative to casing 10 and shell 30. Therefore,movement of locking wedges 74 in a direction perpendicular to thelongitudinal axis of casing 10 is limited, and said locking wedges areretained in the slots 72 in guide member 70 by the wall of opening 52 inpiston 50. As can best be seen in FIGURE 3, when the inner surfaces 76of locking wedges 74 are respectively in contact with surfaces 28 ofprojection 26 the outer surfaces 78 of said locking wedges are inclinedat the same angle with respect to the longitudinal axis of casing 10 asthe wall surfaces of opening 52 in piston 50.

Disposed in vent passage in end wall 32 is a valve, generally designatedby reference number 80, which comprises a first cylindrical portion 82,a second integral cylindrical portion 84 having an increased diameter,and an integral tapered head portion 86 adapted to seat against abeveled edge 88 of said vent passage. The di ameter of portion 84 ofvalve 80 is slightly smaller than the diameter of vent passage 40 sothat when the head portion 86 of the valve is not seated against edge 88(see FIGURE 2) hydraulic fluid or air that may become trapped betweenend wall 32 and piston can pass through said vent passage 40. A Washer90 is seated against the shoulder formed on valve 84 at the junction ofportions 82 and 84 thereof, said washer having a serrated inner edgewhich permits hydraulic fluid or air to flow through vent passage 40 asdescribed immediately hereinbefore. Valve 80 is biased into the openposition thereof illustrated in FIGURE 2 by means of a spring 92 one endof which is positioned within portion 56 of vent passage 54 in piston50.

Disposed in portion 58 of vent passage 54 is a second valve in the formof a ball 94 having a diameter slightly larger than the diameter of themiddle portion of said vent passage. As can best be seen in FIGURE 5,four retaining members 84 are mounted on surface 86 of piston 50 andextend over vent passage 54 so as to hold ball 34 therein.

One use of the described embodiment of the invention is illustrated inFIGURES 2, 3 and 4, wherein casing 10 is mounted on a rigid support (notshown) and spaced a predetermined distance from a worktable 96 againstwhich a workpiece 98 is to be clamped. With piston 50 in the fullyretracted position thereof illustrated in FIGURE 2 and port 22 opened toa hydraulic return line (not shown), port 24 is opened to a highpressure hydraulic line (not shown) to admit fluid pressure into shaft64, shell 30 and the space between end wall 34 of said shell and endclosure 14. This fluid pressure moves ball 94 toward end wall 32,closing vent passage 54 in piston 50, and also moves piston 50 towardend closure 12, bringing the outer face of bulkhead 66 of shaft 64 intoengagement with workpiece 98 (see FIGURE 3). Because of the areadifferential between the faces of end wall 34, the fluid pressure alsomoves shell 30 toward end closure 12. After bulkhead 66 contactsworkpiece 98 fluid pressure continues to drive shell 30 toward endclosure 12 until the outer surfaces 78 of locking wedges 74 respectivelyengage the wall surfaces of opening 52 in piston 50 (see FIGURE 3).Since the space between piston 50 and end closure 12 is not pressurized,spring 92 holds the head portion 86 of valve away from edge 88 of ventpassage 40, and consequently any hydraulic fluid or air trapped betweenpiston 50 and end wall 32 can pass through said vent passage as thedistance between said piston and said end Wall decreases. It will beseen by inspection of FIGURE 3 that after bulkhead 66 contacts workpiece98 any force exerted against shaft 64 which tends to move it toward endclosure 14 causes locking wedges 74 to bind more tightly against thesurfaces 23 of projection 26 and the wall surfaces of opening 52 inpiston 50, thus preventing movement of said piston and said shaft.Furthermore, piston 50 can be locked in any position along its range oftravel within casing 10, and thereafter it is not necessary to maintainfluid pressure within casing 10 in order to hold said piston in saidposition.

To move bulkhead 66 away from workpiece 98, port 24 is opened to thehydraulic return line and port 22 is opened to the high pressurehydraulic line. Fluid pressure thereby admitted into casing 10 betweenend closure 12 and end wall 32 overcomes the force exerted against valve8%) by spring 92 and moves the head portion 86 of said valve againstedge 88 of vent passage 40 to thereby close the latter. The fluidpressure also moves shell 30 toward end closure 14, thus withdrawinglocking wedges 74 from engagement with the wall surfaces of opening 52in piston 50. As shell 30 continues to move toward end closure 14, endwall 32 contacts piston 50 and carries it and shaft 64 connected theretoto their retracted position (see FIGURE 4). Since the space betweenpiston 50 and end closure 14 is not pressurized, any hydraulic fluid orair trapped between end wall 32 and piston 50 forces ball 94 towardretaining members 84 and said hydraulic fluid or air flows through ventpas sage 54 as said end wall moves toward said piston.

It will be recognized that various modifications can be made in thedisclosed fluid pressure actuator and locking device without departingfrom the principles of the invention, the scope of which is limited onlyby the terms of the appended claims. For example, locking wedges 74could be connected to end wall 34 of shell 30 by means of links adaptedto maintain said locking wedges in the proper position relative tosurfaces 28 of projection 26 and at a predetermined distance from saidend wall 34, and also adapted to permit said locking wedges to move in adirection perpendicular to the longitudinal axis of casing 10. Obviouslythe construction and arrangement of the disclosed embodiment of theinvention can also be modified to include more, or fewer, than fourlocking wedges 74. Other changes of similar nature will be readilyapparent to those skilled in the art to which the invention pertains.

What is claimed is:

1. A fluid pressure actuator and locking device comprising:

a tubular casing having first and second end closures respectivelyattached to opposite ends thereof, said first end closure having anaperture formed therein, said casing having a fluid pressure port ateach end thereof;

a projection disposed within said casing and connected at one end tosaid second end closure, at least one surface of said projection beingconvergent with respect to the longitudinal axis of said casing in thedirection of said first end closure;

a tubular shell slidably disposed within said casing, said shell havingfirst and second end walls which are respectively attached to oppositeends thereof and each of which is provided with an aperture throughwhich said projection extends, said first end wall facing said first endclosure and having a vent passage formed therein;

a piston slidably disposed Within said shell, said piston having anopening formed therein which is substantially coaxial with said casingand through which said projection extends, the portion of the wall ofsaid opening that faces said convergent surface of said projection alsobeing convergent with respect to the longitudinal axis of said casing inthe direction of said first end closure, said piston having a ventpassage formed therein;

a tubular shaft slidably disposed in said apertures in said first endwall and said first end closure respectively, said shaft being closed atone end and connected at the other end to said piston so that theinterior thereof communicates with said opening in said piston;

at least one locking Wedge disposed within said shell, said lockingwedge having an inner surface which is disposed adjacent said convergentsurface of said projection and an outer surface which is convergent withrespect to the longitudinal axis of said casing in the direction of saidfirst end closure;

means connected to said shell and adapted to maintain said locking wedgea predetermined distance from said second end wall while permitting itto move in a direction substantially perpendicular to the longitudinalaxis of said casing;

first valve means mounted on said first end wall and adapted to closesaid vent passage therein when fluid pressure is admitted into saidcasing between said first end wall and said first end closure; and

second valve means mounted on said piston and adapted to close said ventpassage therein when fluid pressure is admitted into said casing betweensaid piston and said second end closure.

2. A fluid pressure actuator and locking device comprising:

a cylindrical casing having first and second end closures respectivelyattached to opposite ends thereof, said first end closure having anaperture formed therein, said casing having a fluid pressure port ateach end thereof;

a projection centrally disposed within said casing and connected at oneend to said second end closure, said projection having a plurality ofplanar surfaces each of which is convergent with respect to thelongitudinal axis of said casing in the direction of said first endclosure;

a cylindrical shell slidably disposed within said casing, said shellhaving first and second end Walls which are respectively attached toopposite ends thereof and each of which is provided with an aperturethrough which said projection extends, said first end walls facing saidfirst end closure and having a vent passage formed therein;

a piston slidably disposed within said shell, said piston having anopening formed therein which is substantially coaxial with said casingand through which said projection extends, the wall of said openingincluding a plurality of planar surfaces each of which is convergentwith respect to the longitudinal axis of said casing in the direction ofsaid first end closure, said piston having a vent passage formedtherein;

a cylindrical shaft slidably disposed in said apertures in said firstend wall and said first end closure respectively, said shaft beingclosed at one end and connected at the other end to said piston so thatthe interior thereof communicates with said opening in said piston;

a frustoconical guide member coaxially disposed within said shell andconnected at its large end to said second end wall, said guide memberhaving a plurality of slots formed therein which are spaced apartcircumferentially thereof, said slots being adjacent the free end ofsaid guide member and equidistant from said second end wall, saidprojection extending through said guide member in spaced relationtherewith;

a plurality of locking wedges respectively slidably disposed in saidslots so as to be movable in a direction perpendicular to thelongitudinal axis of said casing, each of said locking wedges having aninner surface Which is disposed adjacent a respective one of saidconvergent planar surfaces of said projection and an outer surface whichis convergent with respect to the longitudinal axis of said casing inthe direction of said first end closure;

first valve means mounted on said first end Wall and adapted to closesaid vent passage therein when fluid pressure is admitted into saidcasing between said first end Wall and said first end closure; and

second valve means mounted on said piston and adapted to close said ventpassage therein when fluid pressure is admitted into said casing betweensaid piston and said second end closure.

References Cited UNITED STATES PATENTS 1,631,369 6/1927 Gartin 92-15 X2,259,815 10/1941 Greve 92-28 X 2,811,951 11/1957 Bodem et a1. 92142,876,746 3/1959 Storrs 92-28 3,050,943 8/1962 Thorel et a1. 92-233,135,171 6/1964 Michalak 92-29 X 3,272,087 9/1966 Culver 9224 MARTIN P.SCHWADRON, Primary Examiner. I. C. COHEN, Assistant Examiner.

1. A FLUID PRESSURE ACTUATOR AND LOCKING DEVICE COMPRISING: A TUBULARCASING HAVING FIRST AND SECOND END CLOSURES RESPECTIVELY ATTACHED TOOPPOSITE ENDS THEREOF, SAID FIRST END CLOSURE HAVING AN APERTURE FORMEDTHEREIN, SAID CASING HAVING A FLUID PRESSURE PORT AT EACH END THEREOF; APROJECTION DISPOSED WITHIN SAID CASING AND CONNECTED AT ONE END TO SAIDSECOND END CLOSURE, AT LEAST ONE SURFACE OF SAID PROJECTION BEINGCONVERGENT WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID CASING IN THEDIRECTION OF SAID FIRST END CLOSURE; A TUBULAR SHELL SLIDABLY DISPOSEDWITHIN SAID CASING, SAID SHELL HAVING FIRST AND SECOND END WALLS WHICHARE RESPECTIVELY ATTACHED TO OPPOSITE ENDS THEREOF AND EACH OF WHICH ISPROVIDED WITH AN APERTURE THROUGH WHICH SAID PROJECTION EXTENDS, SAIDFIRST END WALL FACING SAID FIRST END CLOSURE AND HAVING A VENT PASSAGEFORMED THEREIN; A PISTON SLIDABLY DISPOSED WITHIN SAID SHELL, SAIDPISTON HAVING AN OPENING FORMED THEREIN WHICH IS SUBSTANTIALLY COAXIALWITH SAID CASING AND THROUGH WHICH SAID PROJECTION EXTENDS, THE PORTIONOF THE WALL OF SAID OPENING THAT FACES SAID CONVERGENT SURFACE OF SAIDPROJECTION ALSO BEING CONVERGENT WITH RESPECT TO THE LONGITUDINAL AXISOF SAID CASING IN THE DIRECTION OF SAID FIRST END CLOSURE, SAID PISTONHAVING A VENT PASSAGE FORMED THEREIN; A TUBULAR SHAFT SLIDABLY DISPOSEDIN SAID APERTURES IN SAID FIRST END WALL AND SAID FIRST END CLOSURERESPECTIVELY, SAID SHAFT BEING CLOSED AT ONE END AND CONNECTED AT THEOTHER END TO SAID PISTON SO THAT THE INTERIOR THEREOF COMMUNICATES WITHSAID OPENING IN SAID PISTON; AT LEAST ONE LOCKING WEDGE DISPOSED WITHINSAID SHELL, SAID LOCKING WEDGE HAVIG AN INNER SURFACE WHICH IS DISPOSEDADJACENT SAID CONVERGENT SURFACE OF SAID PROJECTION AND AN OUTER SURFACEWHICH IS CONVERGENT WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID CASINGIN THE DIRECTION OF SAID FIRST END CLOSURE; MEANS CONNECTED TO SAIDSHELL AND ADAPTED TO MAINTAIN SAID LOCKING WEDGE A PREDETERMINEDDISTANCE FROM SAID SECOND END WALL WHILE PERMITTING IT TO MOVE IN ADIRECTION SUBSTANTIALLY PERPENDICULAR TO THE LONGITUDINAL AXIS OF SAIDCASING; FIRST VALVE MEANS MOUNTED ON SAID FIRST END WALL AND ADAPTED TOCLOSE SAID VENT PASSAGE THEREIN WHEN FLUID PRESSURE IS ADMITTED INTOSAID CASING BETWEEN SAID FIRST END WALL AND SAID FIRST END CLOSURE; ANDSECOND VALVE MEANS MOUNTED ON SAID PISTON AND ADAPTED TO CLOSE SAID VENTPASSAGE THEREIN WHEN FLUID PRESSURE IS ADMITTED INTO SAID CASING BETWEENSAID PISTON AND SAID SECOND END CLOSURE.